if([TWTweetComposeViewController canSendTweet])
    {
    TWTweetComposeViewController *tweetSheet = [[TWTweetComposeViewController alloc] init];
    [tweetSheet setInitialText:@"text to send"];
    [tweetSheet addImage:[UIImage imageNamed:@"imageToSend"]];

    [self presentModalViewController:tweetSheet animated:YES];

    tweetSheet.completionHandler = ^(TWTweetComposeViewControllerResult result)  {
      [self dismissModalViewControllerAnimated:YES];
      switch (result) {
        case TWTweetComposeViewControllerResultCancelled:
            break;
        case TWTweetComposeViewControllerResultDone:
            break;
        default:
            break;
       }
     };
   }else
   {
    // you can show alert here
   }